1. Field of Invention
The invention relates to a range switchover apparatus for use in switching of a running range of an automatic transmission.
2. Description of Related Art
Conventionally, a range switchover apparatus for switchover of a running range of an automatic transmission comprises a manual valve in the automatic transmission, and a shift lever connected to the manual valve by a shift cable and provided in the vehicle interior. The range switchover apparatus is structured such that a driver operates the shift lever to thereby switch over the manual valve via the shift cable. However, it has become necessary to increase the freedom in placement of the shift lever as a result of the recent increases in more freedom for vehicle interior design and an increase in the types or models of a car using the same platform.
A range switchover apparatus, which meets with such a demand, is disclosed in Japanese Patent Laid-Open No. 190180/1995. With such a range switchover apparatus, a motor is used to actuate a manual valve to perform switchover of the running ranges, and driving of the switching motor is stopped upon detection of the manual valve being placed in a target position.
However, because conventional range switchover apparatuses are controlled independently of the rotational speed of the switching motor, in the case where the rotational speed of the switching motor is too great, the target position is in some cases passed greatly due to an increase in inertial forces of respective constituent members even when the manual valve stops the switching motor at the target position.
The invention has as its object to provide a range switchover apparatus capable of surely performing the switchover of a switchover means of an automatic transmission.
The above-mentioned problems are solved by a range switchover apparatus for automatic transmissions, according to a first aspect, comprising a range switchover means operating unit capable of switching over a switchover means, which switches over a shift range, among respective shift positions; a detent mechanism for holding the range switchover means operating unit in the respective shift positions; a drive motor for driving the range switchover means operating unit; a driving force stopping unit for preventing a driving force from the drive motor from being transmitted to the range switchover means operating unit; a stoppage controlling unit adapted to detect a position of the range switchover means operating unit to control the driving force stopping unit so as to hold the range switchover means operating unit in a predetermined shift position; an environment detecting unit for detecting an environment of the drive motor; and a rotation controlling unit for controlling the drive motor at a predetermined rotational speed in response to a state of the environment detected by the environment detecting unit.
The invention according to a second aspect comprises a range switchover apparatus for automatic transmissions wherein the detent mechanism comprises a plurality of recesses provided on the range switchover means operating unit to correspond to the shift positions, and an engagement member capable of selectively engaging with and disengaging from the recesses, and the engagement member detects a position corresponding to an inlet of a recess corresponding to the predetermined shift position whereby the stoppage controlling unit transmits a stoppage signal to the driving force stopping unit.
The invention according to a third aspect comprises a range switchover apparatus for automatic transmissions wherein the driving force stopping unit stops the drive motor and actuates a brake.
The invention according to a fourth aspect comprises a range switchover apparatus for automatic transmissions wherein the driving force stopping unit comprises a clutch for cutting off a driving force from the drive motor to the switchover means driving unit.
The invention according to a fifth aspect comprises a range switchover apparatus for automatic transmissions wherein the environment detecting unit comprises a voltage measuring device for measuring an electric source voltage of the drive motor.
The invention according to a sixth aspect comprises a range switchover apparatus for automatic transmissions wherein the environment detecting unit comprises a temperature measuring device for measuring an oil temperature in the automatic transmission.